The Volvo STD 420-0001 “Assessment of the degree of paint blistering - Paints and enamels” standard, developed by Volvo, describes a test method designed to determine the degree of blistering in paint coatings on parts tested or used under accelerated or atmospheric conditions. In terms of its technical content, this standard conforms to the “EN ISO 4628-2 Paints and varnishes - Assessment of coating degradation - Determination of the quantity and size of defects and the intensity of uniform variations in appearance - Part 2: Assessment of the degree of blistering” standard. Furthermore, this standard indicates the grading scale used in the “ASTM D714-02 Standard test method for assessing the degree of blistering of paints” standard.
The density and size of the blisters are evaluated by comparison with photographic reference standards. These photographic reference standards show blisters of densities 2, 3, 4, and 5, and sizes 2, 3, 4, and 5 for each density. If the rating for density or size is less than 2, the rating is 1.
The photographic representations given in this standard should not be used as photographic reference standards. Photographic reference standards can be requested from the link below each image. These photographic reference standards are for Volvo Group internal use only. The relationship between ISO's rating system and ASTM's rating system is given in the table given in the standard.
The report to be prepared upon completion of the tests should include:
For example, if the evaluation shows that the bubble density is 2 and the size is 2, the rating in this case is "Bubble 2 (S2)".
When bubbles of varying sizes are seen in a test area, the size rating should be determined as the largest number of bubbles that are specific to the test area.
Paint bubbles can develop long after the paint on your vehicle has dried. Paint bubbles occur when the paint film lifts off the underlying surface. The loss of adhesion between the paint film and the surface is usually caused by heat, moisture, or a combination of both. This eventually leads to peeling. This can be fixed, but the underlying cause must be addressed or the problem will reoccur.
Paint blistering or bubbling can occur for a variety of reasons: painting on a damp, dirty or hot surface, applying oil-based or alkyd paint over latex paint, improper surface preparation, excessive humidity, and exposing the paint to moisture shortly after it has dried. Bubbles form when moisture escapes from the film as humidity decreases and temperatures increase. The pressures created in the film are enormous and are often sufficient to cause the paint film to bubble.
The cause of blistering is the saturation of the film with exceptionally high levels of atmospheric moisture and the presence of water-soluble substances (sometimes primers). These are either absorbed into the film or are present on the surface before painting. As moisture decreases and temperature increases, blisters form when moisture escapes from the film. At very low temperatures, the moisture freezes in the film. This leads to weaknesses in adhesion, making subsequent blistering much more likely. When water vapor penetrates the paint film, it can create a force sufficient to weaken the adhesion between paint layers or even the adhesion between the entire paint process and the metal.
Among the numerous tests, measurements, analyses and evaluations carried out for businesses in various sectors, our organization also provides testing services defined in the “Volvo STD 420-0001 Evaluation of paint swelling degrees - Paints and enamels” standard with its trained and expert staff and advanced technological equipment.
To get an appointment, to get more detailed information or to request an evaluation, you can ask us to fill in our form and reach you.
